In recent years, a distributed control system is employed which connects through a network and collectively controls distributed sensors and actuators in a single system to reduce the wiring for an industrial apparatus or a factory automation (FA) system.
The distributed control system generally includes a central communication unit and a plurality of terminal communication units. The central communication unit provides integrated control of an overall sequence. The terminal communication units provide input/output control of the sensors and actuators.
In the distributed control system, a network is formed between the central communication unit and the terminal communication units.
The network is generally formed, for example, of a multi-drop topology or a daisy chain topology.
The central communication unit transfers control information to the terminal communication units through the network. The terminal communication units exercise input/output control of the sensors and actuators in accordance with the control information.
In addition, the terminal communication units transfer control information input from the sensors and actuators to the central communication unit through the network.
As described above, the distributed control system transmits and receives the control information between the central communication unit and the terminal communication units through the network so that the central communication unit can provide overall control of the distributed sensors and actuators.
Meanwhile, it is demanded in industrial fields that a control system using many sensors and actuators should have improved performance, for instance, by providing high speed and high accuracy.
The improvement of the performance of the above-mentioned control system may be obstructed by the response performance of a network for the distributed control system. If the network's response performance is low, the improvement of the performance of the above-mentioned control system is significantly obstructed. Therefore, it is desired that the response performance of the network should be as high as possible.
However, as common characteristics of the distributed control system, the response performance of the network deteriorates when the number of the sensors and actuators to be controlled increases.
Therefore, special communication control methods are explored for the network in the distributed control system so that the response performance is maintained as high as possible for the control of many sensors and actuators.
As a relevant related-art technology, for instance, JP 2006-209646 discloses a technology in which a synchronization signal is transmitted to all the external instruments when all the external instruments are confirmed ready for operation.
However, the technology described in JP 2006-209646 does not provide measures against an increase in the adjustment and setup steps of communication control. Therefore, it is difficult for the above-mentioned related-art technology to reduce the adjustment and setup steps required when the distributed control system is applied to a control system including many sensors and actuators.
The present invention has been made in view of the above circumstances to provide a distributed control system that is capable of automating adjustment and setup for communication control when the distributed control system is applied to a control system including many sensors and many actuators.
The present invention has also been made to provide a communication control system that automates the adjustment and setup for communication control to achieve required performance of the control system including many sensors and many actuators.